Fat but healthy: is it a real thing?

Central Obesity

I cannot count the number of times that a patient or family member has said that they are fat but healthy.  As a physician, I have no idea what that means, but it seems to be a common myth.  I guess, the basic belief is that it is healthier to be an overweight person that has a good cholesterol and lab values who is moderately active than a slim person with elevated cholesterol and never exercises.  This concept has little to no research to back it up until now, and the research directly contradicts this belief.  

The concept that some individuals are metabolically healthy despite being obese or morbidly obese has been with us for nearly 40 years.   It was first described in the early 1980s[1].   A recent study found that this population is approximately 20% of the population appears to have this genetic protection against some of the metabolic complication of obesity[2] I think it important that we challenge this notion which is exactly what more recent research is doing.  This concept is reckless because many people believe incorrectly that is the are in this small group that they do not have to lose weight and that weight loss would not make them more healthy.  Nothing could be further from the truth.  Just because they do not get the same degree of benefit from weight loss, they still get some.  

Let’s start off with a few definitions.  

1. 1. 

      Obesity Kills

      Metabolically healthy obesity (MHO): It is controversial and is characterized by obesity which does not produce metabolic complications.  The metabolic complications include dyslipidemia such as low HDL (good cholesterol) and high LDL (bad cholesterol), insulin resistance, elevated blood glucose, and metabolic syndrome.  Metabolically healthy obesity is characterized by having a lower visceral adipose tissue or central obesity, so they have an elevated BMI, but do not have an enlarged waist circumference.  This statement may result in an elevated BMI.  The risk for diabetes and heart disease of these individuals does not improve significantly when weight is lost.  They also often exercise regularly.  

   2. Metabolically unhealthy obesity (MUO): This condition is characterized by obesity which the patient has metabolic complications.  Metabolically unhealthy obesity is characterized by having more visceral adipose tissue or central obesity.  They classically have an increased waist circumference and elevated BMI.  Weight loss does improve metabolic risk for heart disease and diabetes.  They often do not exercise regularly.
   3. Metabolically unhealthy lean (MUL): This condition is characterized by having a normal weight which the patient has metabolic complications.  Metabolically unhealthy lean is characterized by having more visceral adipose tissue or central obesity but a normal weight.  They often have a lower muscle mass and do not exercise regularly.  They classically have an increased waist circumference and elevated BMI.  Weight loss does improve metabolic risk for heart disease and diabetes. 
   4. Metabolically healthy lean (MHL): This condition is characterized by having a normal weight which the patient does not have metabolic complications.  Metabolically healthy lean is characterized by having the normal visceral adipose tissue level or normal body fat level.  They often have a higher muscle mass and do exercise regularly.  They classically have a normal waist circumference and BMI.  

Some recent research suggests that MHO individuals are at an increased risk of several adverse outcomes.  The negative outcomes include type 2 diabetes, depressive symptoms, cardiovascular and hypertensive events, and strokes.  Research also suggests that although MHO individuals display a favorable metabolic profile, this does not necessarily translate into a decrease in mortality.  Honestly, research to date has produced conflicting results concerning cardiovascular disease and mortality.  MHO individuals are at a higher risk of heart disease compared to metabolically healthy non-obese individuals, but they are also at a lower risk thereof than people who are both unhealthy and obese.  

The Evidence:

1. 

   Five obesely fat men on the beach

   Obesity is a risk for increased cardiovascular and all cause mortality.  A 2016 meta-analysis looked at obese and overweight individuals and their risk of all-cause mortality and cardiovascular casues[3].   Overweight and obesity is associated with increased risk of all cause mortality and the lowest risk was observed at BMI of 23-24.  The relatively low risk of cardiovascular disease among people with MHO relative to metabolically unhealthy obese people has been attributed to differences in white adipose tissue function between the two groups.  

2. MHO is partially protective against heart disease[4].  It is clear that there is some degree of protection offered by being MHO over MUL and MUO.  It is also clear that being MHU is not as good as being MHL.  You can throw this all out the window if you smoke, but being obese and smoking is like putting out the fire with gasoline.  MHO is still at a higher risk of Cardiovascular disease than MHL.  
3. MHO might not be as healthy as we thought.  According to a meta-analysis from 2013[5] that compared with metabolically healthy normal-weight individuals, obese persons are at increased risk for adverse long-term outcomes even in the absence of metabolic abnormalities. This concept suggests that there is no healthy pattern of increased weight.  This result was confirmed by a 2015 study[6] that found that the MHO phenotype is associated with a lower risk of For type 2 diabetes than the metabolically unhealthy obese, but has a higher risk of  CVD is linked to both obesity phenotypes.

Recommendations:

1. 

   Obesity – Fat Belly

   Individualize your weight loss goals.  Bone and muscle mass vary so you should make a weight goal that is realistic.  Use waist circumference with a scale instead of just a scale or BMI.  

2. You may have a normal weight but higher risk of cardiovascular disease and diabetes.  This study clearly indicates that an individual with normal weight may have two or more parameters of the metabolic syndrome, and thus an elevated risk of diabetes or cardiovascular disease.  
3. Cardiometabolic disease, such as type 2 diabetes or cardiovascular disease, can be present in very lean people.  I see this all the time.  This outcome is often seen with less leg muscle mass or “chicken legs.”   

The bottom line:  This belief of healthy but obese is not legitimate and has little evidence to back it up.  They may have a lower risk that unhealthy obese individual or the unhealthy lean, but I suspect they will acquire the disease quicker than the healthy lean.  BMI is not a good measure of body fat percentage, but an elevated BMI is associated with an increase in disease.  I recommend that you look at lowering your body fat percentage and waist circumference.  Your waist is a great measure of unhealthy body fat and it easy to do.